The present invention relates to bisimidine compounds, a process for their preparation, bisimidinato complexes as catalysts, a process for preparing them and their use in the polymerization of unsaturated compounds.
There is great interest in the development of novel families of catalysts for the polymerization of unsaturated compounds in order to obtain better control over the properties of polyolefins or further novel products.
Use of transition metal compounds as catalytically active substances for the polymerization of unsaturated compounds has been known for a long time. For example, Ziegler-Natta or Phillips catalysts are used commercially for the synthesis of polyolefins. More recently, metallocenes are being used as highly active polymerization catalysts. The metallocenes make it possible to obtain polymers having a narrow molecular weight distribution and copolymers having a uniform comonomer content.
However, metallocene catalysts have disadvantages for industrial use. For example, they are very sensitive to impurities in commercially available monomers, in the process gas and in the solvents used and to hydrolysis. Furthermore, the price of metallocenes having zirconium as central metal is very high.
It has been known for some time that new types of iron and cobalt complexes containing bisimidine ligands are very active as catalysts in the polymerization of unsaturated compounds.
V. C. Gibson et al., Chem. Commun. 1998, 849-850, and M. Brookhart et al., J. Am. Chem. Soc. 1998, 120, 4049-4050, disclose new olefin polymerization catalysts based on Fe(II) and Co(II). These catalysts contain 2,6-bis(imino)pyridyl ligands which are aryl-substituted on the imino nitrogens and display high activities in the polymerization of ethylene. The polyethylene obtained is essentially linear and the molecular weight is strongly dependent on the substituents on the alkyl radical.
WO 99/12981 describes bisimidinato complexes, their synthesis and their use in the polymerization of unsaturated compounds. Numerous complexes having a variety of different radicals are disclosed. 
Examples 30 and 31 disclose complexes of the formula A in which R=CH3 and C6H5. However, the demonstrated activities in the polymerization of ethylene are much too low for industrial applications.
It is an object of the present invention to provide novel complexes containing a metal of groups 7, 8, 9 or 10 of the Periodic Table of the Elements (late transition metal) as central metal which can be used for the polymerization of unsaturated compounds and give branched polymers in the polymerization. This object can be subdivided into the provision of a ligand system for this catalyst and a process for preparing this ligand system and the provision of a process for preparing the corresponding catalyst.
We have found that this object is achieved by compounds of the formula (I) 
where the symbols have the following meanings:
A is a nonmetal selected from among N, S, O and P,
R1 is a radical of the formula NR5R6,
R2 is a radical of the formula NR5R6 or NR7R8, where R5 and R6 are selected from among alkyl, aryl and cycloalkyl, and
R5 and R6 together with the N atom form a 5-, 6- or 7-membered ring in which one or more of the xe2x80x94CHxe2x80x94 or xe2x80x94CH2xe2x80x94 groups may be replaced by suitable heteroatom groups and which may be saturated or unsaturated and unsubstituted or substituted or be fused with further carbacyclic or heterocarbacyclic 5- or 6-membered rings which may in turn be saturated or unsaturated and substituted or unsubstituted, and
R7 and R8 are, independently of one another, alkyl, aryl or cycloalkyl radicals, and
R3, R4 are, independently of one another, H or alkyl, aryl or cycloalkyl radicals, and
n is 1 or 2.
The bisimidines of the present invention have at least one nitrogen-nitrogen bond to at least one of the two imine nitrogens as [xe2x95x90Nxe2x80x94NR5R6], where the substituents R5 and R6 together form a cyclic substituent.
These compounds are particularly useful as ligand systems for preparing novel, efficient catalyst systems for the polymerization or copolymerization of unsaturated compounds. These novel ligands are simple to prepare and make it possible to vary the radicals within a wide range. This system is therefore very variable and allows the ligand and complex systems to be tailored to various applications. Use of compounds of the formula (I) as ligand system makes it possible to obtain highly active catalysts for the polymerization of unsaturated compounds.
Above and in the following, alkyl radicals are generally linear or branched C1-C20-alkyl radicals, preferably C1-C10-alkyl radicals, particularly preferably C1-C8-alkyl radicals. These alkyl radicals can be substituted by heteroatoms. Suitable alkyl radicals are, for example, methyl, i-propyl, t-butyl, trifluoromethyl and trimethylsilyl radicals.
Aryl radicals are generally unsubstituted and substituted C6-C20-aryl radicals (the number of carbon atoms refers to the carbon atoms in the aryl radical), preferably C6-C14-aryl radicals, which may be unsubstituted or bear one or more substituents; very particularly preference is given to C6-C10-aryl radicals, substituted by C1-C6-alkyl radicals, e.g. 4-methylphenyl, 2,6-dimethylphenyl, 2,6-diethylphenyl, 2,6-diisopropylphenyl, 2-tert-butylphenyl, 2,6-di(tert-butyl)phenyl or 2-i-propyl-6-methylphenyl. The aryl radicals can also be substituted by heteroatoms, e.g. by F.
Cycloalkyl radicals are generally C5-C8-cycloalkyl radicals (the number of carbon atoms refers to the carbon atoms in the cycloalkyl ring) which may be unsubstituted or substituted by one or more alkyl or aryl radicals or heteroatoms. Preference is given to C5-C6-cycloalkyl radicals.
In the compounds of the present invention, R5 and R6 together with the N atom form a 5-, 6- or 7-membered ring in which one or more of the xe2x80x94CHxe2x80x94 or xe2x80x94CH2xe2x80x94 groups may be replaced by suitable heteroatom groups. Suitable heteroatom groups are preferably xe2x80x94Nxe2x80x94 or xe2x80x94NHxe2x80x94 groups. Particular preference is given to from 0 to 3 xe2x80x94CHxe2x80x94 or xe2x80x94CH2xe2x80x94 groups being replaced by xe2x80x94Nxe2x80x94 or xe2x80x94NHxe2x80x94 groups.
The 5-, 6- or 7-membered ring can be saturated or unsaturated. In the latter case, the ring may be monounsaturated or polyunsaturated. Preference is given to unsaturated 5-membered rings. For the purposes of the present invention, unsaturated rings include, in the case of the 5-membered rings, aromatic rings such as unsubstituted or substituted pyrrole radicals and derivatives thereof, which are particularly preferred.
The 5-, 6- or 7-membered ring may be unsubstituted, substituted or fused with further carbacyclic or heterocarbacyclic 5- or 6-membered rings which may in turn be saturated or unsaturated and substituted or unsubstituted.
For the purposes of the present invention, carbacyclic rings are rings whose skeleton is made up entirely of carbon. In the heterocarbacyclic rings, one or more xe2x80x94CH2xe2x80x94 or xe2x80x94CHxe2x80x94 groups are replaced by heteroatoms, preferably xe2x80x94NHxe2x80x94 or xe2x80x94Nxe2x80x94 groups. Particular preference is given to carbacyclic rings or heterocarbacyclic rings having a nitrogen atom in the ring system.
Possible substituents in these carbacyclic and heterocarbacyclic 5- or 6-membered rings are the abovementioned alkyl, aryl or cycloalkyl radicals. The rings may bear one or more substituents. Preference is given to from 1 to 3 substituents. Furthermore, the ring systems may be orthofused or orthofused and perifused. The system is preferably orthofused, with particular preference being given to 1 or 2 phenyl radicals being fused onto the central 5- or 6-membered ring, e.g. indole, carbazole and derivatives thereof.
In a particularly preferred embodiment, the ring described by the formula NR5R6 is 5-membered. Very particular preference is given to an unfused 5-membered ring, in particular a pyrrole radical or a radical derived from pyrrole, in which no, one or more, preferably from 0 to 3, particularly preferably 0 or 2, xe2x80x94CHxe2x80x94 groups in the pyrrole ring may be replaced by nitrogen. Examples are the pyrrole system and the triazole system. Particular preference is given to pyrrole radicals or radicals derived from pyrrole which are substituted in the 2 and 5 positions by: C1-C6-alkyl groups which may be linear, branched and substituted by heteroatoms, or electron-withdrawing radicals such as halogen, nitro, sulfonate or trihalomethyl.
Suitable sulfonate radicals are, in particular, SO3R*, SO3Si(R*)3 and SO3xe2x80x94(HN(R*)3)+. Among these, SO3Me, SO3SiMe3 and SO3xe2x80x94(HNEt3)+ are particularly useful. Among the trihalomethyl radicals, trifluoromethyl, trichloromethyl and tribromomethyl, especially trifluoromethyl are particularly useful. Particularly useful ortho substituents are halogen radicals such as fluorine, chlorine, bromine or iodine. Preference is given to using chlorine or bromine as ortho substituents. Furthermore, the respective ortho positions are preferably occupied by identical radicals. Aryl groups may be unsubstituted or substituted in turn by C1-C6-alkyl groups which may be heteroatom-substituted. Preferred substituents in the 2 and 5 positions of the pyrrole ring or a derivative thereof, preferably triazole, are methyl-, i-propyl-, t-butyl- and phenyl-substituted aryl radicals, as defined above.
According to the present invention, R3 and R4 in the formula (I) can be, independently of one another, H or alkyl, aryl or cycloalkyl radicals, with preferred radicals having been defined above. R3 and R4 are very particularly preferably, independently of one another, H or CH3.
According to the present invention, R* can be H, alkyl, aryl or cycloalkyl, with preferred radicals having been defined above. R* is very particularly preferably CH3 or H.
Preference is given to using compounds of the formula (I) in which A=N or S. A is particularly preferably N. The central ring is preferably a 6-membered ring, i.e. n is preferably 2. Thus, pyridinebisimidine systems are very particularly preferred.
Particular preference is given to compounds of the formulae (Ia) to (Id): 
where R3, R4, R9 and R10 are, independently of one another, C1-C20-alkyl radicals which may be linear or branched, preferably C1-C10-alkyl radicals, particularly preferably C1-C6-alkyl radicals. These alkyl radicals may be heteroatom-substituted. Suitable alkyl radicals are, for example, methyl, i-propyl, t-butyl, trifluoromethyl and trimethylsilyl radicals. The radicals Rxe2x80x2, Rxe2x80x3, Rxe2x80x2xe2x80x3 and Rxe2x80x3xe2x80x3 are H or alkyl, aryl or cycloalkyl radicals, as defined above.
The novel compounds of the formula (I) 
where
R1 is a radical of the formula NR5R6,
R2 is a radical of the formula NR5R6, NR7R8 or an alkyl, aryl or cycloalkyl radical,
and the other symbols are as defined above, are generally prepared by condensation of the corresponding amino compounds with the corresponding diketo compounds, e.g. 2,5-diformylthiophene or 2,6-diacetylpyridine. They are very readily synthesized and it is possible to synthesize a large number of different compounds of the formula (I) in good yields.
The preferred method of preparation is dependent on the desired compound of the formula (I). In the following, a description is given of preferred embodiments for preparing symmetrical compounds of the formula I in which R1=R2=NR5R6 and unsymmetrical compounds of the formula I in which R1+R2 and R2 is a radical of the formula NR5R6 which is different from R1 which is a radical of the formula NR7R8 or an alkyl, aryl or cycloalkyl radical.
In a preferred embodiment, symmetrical compounds of the formula (I) in which R1=R2 are prepared by reacting compounds of the formula (II)
H2Nxe2x80x94NR5R6xe2x80x83xe2x80x83(II)
where
R5 and R6 are as defined above,
with diketo compounds of the formula (III), 
where
R3, R4 are, independently of one another H or alkyl, aryl or cycloalkyl radicals, and
A is S, N, O or P, and
n is 1 or 2.
The process is carried out in one step under acidic reaction conditions, preferably with addition of a mineral acid or an organic acid, particularly preferably formic acid, in alcoholic solvents, preferably in methanol. Alternatively, the process can be carried out in the presence of a trialkylaluminum catalyst, preferably trimethylaluminum, in an aprotic solvent, preferably in toluene. The ratio of the compound of the formula (II) to the compound of the formula (III) is 2:0.7-1.3, preferably 2:0.9-1.1, particularly preferably 2:1. The reaction under acidic conditions in methanol/formic acid is generally preferred.
In general, the condensation is carried out at from 0 to 100xc2x0 C., preferably from 15 to 80xc2x0 C., particularly preferably from 20 to 40xc2x0 C. The reaction time is generally from 20 minutes to 48 hours, preferably from 1 hour to 16 hours, particularly preferably from 2 hours to 14 hours. The precise reaction conditions are dependent on the compounds used in each case. In the case of compounds of the formulae (II) and (III) which condense only slowly to form the desired compounds of the formula (I), reaction in the presence of a trialkylaluminum catalyst in aprotic solvents may be preferred.
In a further preferred embodiment, the unsymmetrical 1,2-diimines of the formula (I) in which R1xe2x89xa0R2 are prepared in a two-stage process in which
a) in a first step, compounds of the formula (II)
N2Nxe2x80x94NR5R6xe2x80x83xe2x80x83(II)
where
R5 and R6 are as defined above are reacted with diketo compounds of the formula (III) 
xe2x80x83where
R3, R4 are, independently of one another, H or alkyl, aryl or cycloalkyl radicals, and
A is S, N, O or P, and
n is 1 or 2,
in a ratio of the compounds of the formula (II) to the compounds of the formula (III) of 1:0.8-1.2, preferably 1:0.9-1.1, particularly preferably 1:1, under acidic conditions, preferably with addition of mineral acids or organic acids, particularly preferably formic acid, in alcoholic solution, preferably methanol, to form the corresponding monoimine and the solvent is subsequently removed under reduced pressure, and
b) the monoimine is, in a second step, reacted with compounds of the formula (II) which differ from the compounds of the formula (II) used in step a) or
with compounds of the formula (IV)
H2Nxe2x80x94RN7R8xe2x80x83xe2x80x83(IV)
where
R7 and R8 are, independently of one another, alkyl, aryl or cycloalkyl radicals, or
with amines of the formula (V)
R13-NH2xe2x80x83xe2x80x83(V)
where
R13 is an alkyl, aryl or cycloalkyl radical, as defined above,
in aprotic solution, preferably in toluene, in the presence of a trialkylaluminum catalyst, preferably trimethylol aluminum, in a ratio of the monoimine to the compound of the formula (II), (IV) or (V) of 1:0.8-1.2, preferably 1:0.9-1.1, particularly preferably 1:1.
In general, the condensation in step a) is carried out at from 0 to 100xc2x0 C., preferably from 15 to 80xc2x0 C., particularly preferably from 20 to 40xc2x0 C. The reaction time is generally from 20 minutes to 48 hours, preferably from 1 hour to 16 hours, particularly preferably from 2 hours to 14 hours. The precise reaction conditions are dependent on the compounds used in each case. Step b) is generally carried out at from 0 to 100xc2x0 C., preferably from 20 to 80xc2x0, particularly preferably from 30 to 60xc2x0 C. The reaction time is generally from 20 minutes to 48 hours, preferably from 1 hour to 8 hours, particularly preferably from 2 hours to 7 hours. The precise reaction conditions are once again dependent on the compounds used in each case.
As compounds of the formula (II)
H2Nxe2x80x94NR5R6xe2x80x83xe2x80x83(II)
where
R5 and R6 are as defined above,
particular preference is given to using compounds in which the group NR5R6 is a pyrrole radical or a radical derived from pyrrole which is very particularly preferably substituted in the 2 and positions by C1-C6-alkyl groups which may be linear, branched and be heteroatom-substituted, and/or by aryl groups which may be unsubstituted or in turn substituted by C1-C6-alkyl groups which may be heteroatom-substituted. Preferred substituents in the 2 and 5 positions of the pyrrole ring are methyl, i-propyl, t-butyl, phenyl or substituted aryl radicals, as defined above.
Such N-amino pyrroles can be obtained, for example, by the following two-stage process:
i) reaction of a suitable 1,4-diketone with an equivalent amount of acetylhydrazine or benzoyloxycarbonylhydrazine in the presence of a catalytic amount of acid, preferably p-toluenesulfonic acid, in an inert organic solvent, preferably toluene, to form the corresponding acetyl- or benzoyloxycarbonyl-protected N-aminopyrrole;
ii) hydrolysis of the protected N-aminopyrrole by means of an excess of base, preferably potassium hydroxide, in a high-boiling inert organic solvent, preferably ethylene glycol, under reflux to give the corresponding free N-aminopyrrole.
The subsequent work-up is carried out in a customary fashion.
The diketo compounds used in the process of the present invention are compounds of the formula (III); 
where
R3, R4 are, independently of one another, H or alkyl, aryl or cycloalkyl radicals, with preferred radicals having been defined above; R3 and R4 are very particularly preferably H or CH3; and
A is S, N, O or P, preferably N or S, particularly preferably N, and
n is 1 or 2, preferably 2.
The central heteroaromatic unit of the compounds of the formula (III) is thus preferably a pyridine ring which is substituted in the 2 and 6 positions.
The compounds of the present invention are suitable as ligands for catalysts which can be used for the polymerization of unsaturated compounds. The compounds of the present invention are particularly useful as ligands for catalysts containing a late transition metal, e.g. containing a metal of group 7, 8, 9 or 10 of the Periodic Table of the Elements. The present invention therefore also provides compounds of the formula (VI), 
where the symbols have the following meanings:
A is a nonmetal selected from among N, S, O and P,
R1 is a radical of the formula NR5R6,
R2 is a radical of the formula NR5R6 or NR7R8, alkyl, aryl or cycloalkyl,
R5 and R6 together with the N atom form a 5-, 6- or 7-membered ring in which one or more of the xe2x80x94CHxe2x80x94 or xe2x80x94CH2xe2x80x94 groups may be replaced by suitable heteroatom groups and which may be saturated or unsaturated and unsubstituted or substituted or be fused with further carbacyclic or heterocarbacyclic 5- or 6-membered rings which may in turn be saturated or unsaturated and substituted or unsubstituted, and
R7 and R8 are, independently of one another, alkyl, aryl or cycloalkyl radicals, and
R3, R4 are, independently of one another, H or alkyl, aryl or cycloalkyl radicals,
n is 1 or 2,
M is a transition metal of groups 7, 8, 9 or 10 of the Periodic Table of the Elements, and
X is a halide or a C1-C6-alkyl radical and
m is the valence of the metal, preferably 2 or 3.
The transition metal M of group 7, 8, 9 or 10 of the Periodic Table of the Elements is preferably Ru, Mn, Co, Fe, Ni or Pd. These metals can be used in the following valences: Fe(II), Fe(III), Co(I), Co(II), Co(III), Ru(II), Ru(III), Ru(IV), Mn(I), Mn(II), Mn(III), Mn(IV), Ni(II), Pd(II). Particular preference is given to Fe and Co and m=2. The ligands X can be, independently of one another, halides or alkyl radicals. They are preferably chloride, bromide or methyl radicals. Particularly preferred moieties MXm are MnCl2, FeCl3, CoCl3, PdCl2, NiCl2, CoCl2, FeCl2.
Preferred radicals R1, R2, R3 and R4 are as defined above.
Very particular preference is given to compounds of the formulae (VIa) to (VId): 
where
R3, R4 are, independently of one another, H or alkyl or aryl radicals, with preferred radicals having been defined above, and
R9, R10, R11 and R12 are, independently of one another, C1-C6-alkyl radicals, with preferred radicals having been defined above, and
Rxe2x80x2, Rxe2x80x3, Rxe2x80x2xe2x80x3, Rxe2x80x3xe2x80x3 are H or alkyl, aryl or cycloalkyl radicals, with preferred radicals having been defined above, and
MX2 is MnCl2, CoCl2 or FeCl2, particularly preferably FeCl2 and CoCl2.
After activation with an activator (cocatalyst), these complexes are highly active in the polymerization of unsaturated compounds. The polymers obtained display a strong dependence on the structure of the ligand. Thus, small variations in the ligand make it possible to obtain a large number of catalytically active compounds which allow the preparation of polymers and oligomers having a wide spectrum of different properties.
The novel compounds of the formula (VI) are usually prepared by reacting the corresponding compounds of the formula (I) with salts of transition metals of groups 7, 8, 9 and 10 of the Periodic Table of the Elements.
In a preferred embodiment, a compound of the formula (I) which is suitable as ligand is combined in an organic solvent, e.g. tetrahydrofuran (THF) or methylene chloride, with an appropriate metal salt, e.g. MnCl2, FeCl3, CoCl3, CoCl2, NiCl2, PdCl2, FeCl2, FeCl2-THF complex. The molar ratio of ligand to metal salt is generally from 1.5:1 to 1:1.5, preferably from 1.2:1 to 1:1.2, particularly preferably about 1:1. The reaction mixture is generally stirred at temperatures from room temperature to 50xc2x0 C., preferably from room temperature to 40xc2x0 C., particularly preferably at room temperature, for generally from 0.5 hour to 16 hours, preferably from 1 to 6 hours, particularly preferably from 1 to 3 hours. The work-up is carried out in a customary manner, e.g. by removing the solvent under reduced pressure, washing of the residue with an inert solvent in which the residue (product) is largely insoluble, e.g. with diethyl ether, if desired digestion in a nonpolar solvent, e.g. hexane, filtration, washing and drying.
The novel metal complexes of the formula (VI) can be obtained easily and are suitable as catalysts for the polymerization of unsaturated compounds. They display a surprisingly high productivity in the polymerization or copolymerization of unsaturated compounds. Furthermore, in copolymerization, a number of the novel complexes enable a high incorporation of comonomer to be achieved. Even slight variations in the ligand skeleton of the metal complex enable the preparation of a wide range of polymers having different properties, so that it is possible to xe2x80x9ctailorxe2x80x9d a catalyst for a polymer having the desired properties.
For example, if iron complexes with 2,5-diisopropylpyrrole ligands are chosen, the polymerization of ethylene gives polymers having a relatively high molar mass in the region of Mw=about 105.
Use of 2,5-dimethylpyrrole complexes of iron in the polymerization of ethylene at room temperature and atmospheric pressure gives oligomers having an M, of from 3000 to 3500 g/mol (determined by gel permeation chromatography (GPC)) and a molar mass distribution of Q=2-5, preferably Q=2-3, which is narrow for single-site catalysts. A particular feature of these oligomers is their unusual structure. They display a particularly high degree of branching, which can also be observed in the homopolymerization of ethylene. The very high proportion of branches longer than 6 carbon atoms is particularly conspicuous. In the case of other catalyst systems (i.e. other than the catalyst systems of the present invention) which give polyolefins having a high degree of branching (e.g. Ni- and Pd-diimine systems), methyl branches are by far the most abundant and only a small number of longer branches is present. Furthermore, the oligomers prepared according to the present invention also have a large number of unsaturated end groups which make it possible for them to be used as monomers in polymerizations or to be functionalized chemically.
Variation of the ligand, e.g. iron complex having a carbazole substituent, enables relatively short-chain oligomers (liquids) to be obtained.
Other catalyst systems, e.g. Co complexes containing carbazole groups, give only very short-chain oligomers which generally have from 6 to 18 carbon atoms, preferably a maximum of 8 carbon atoms.
In the copolymerization of a-olefins, the use of, for example, an iron-isopropylmethylpyrrole system gives excellent incorporation of, for example, hexene.
A simple variation of the ligand framework thus provides catalysts for preparing a wide variety of polymers. In addition, these catalysts display a very high activity which in many cases exceeds that of comparable systems. Furthermore, cobalt complexes having an extremely high activity have been found. The activity of Co complexes known from the literature is usually at least a factor of ten less than that of analogous Fe complexes (V. C. Gibson et al., Chem. Commun. 1998, 849-850 and M. Brookhart et al., J. Am. Chem. Soc. 1998, 120, 4049-4050).
Accordingly, the present invention further provides for the use of compounds of the formula (VI) as catalysts in a process for the polymerization of unsaturated compounds and provides a process for preparing polyolefins by polymerization of unsaturated compounds in the presence of a catalyst according to the present invention and an activator.
Particularly useful activators (cocatalysts) are strong, uncharged Lewis acids, ionic compounds having Lewis acid cations and ionic compounds having Bronsted acids as cations.
As strong, uncharged Lewis acids, preference is given to compounds of the formula (VII),
Mxe2x80x2X1X2X3xe2x80x83xe2x80x83(VII)
where the symbols have the following meanings:
Mxe2x80x2 is an element of main group III of the Periodic Table of the Elements, preferably B, Al or Ga, particularly preferably B,
X1, X2, X3 are each, independently of one another, hydrogen, C1-C10-alkyl, C6-C15-aryl, alkylaryl, arylalkyl, haloalkyl or haloaryl each having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, or fluoride, chloride, bromide or iodide; preference is given to haloaryls, particularly preferably pentafluorophenyl.
Very particular preference is given to compounds of the formula (VII) in which X1, X2, X3 are identical, preferably tris(pentafluorophenyl)borane.
A further preferred uncharged Lewis acid for use as activator (cocatalyst)) is xe2x80x9cR14AlOxe2x80x9d (alkylaluminoxane), where R14 is a C1-C25-alkyl radical, preferably a C1-C4-alkyl radical, particularly preferably a methyl radical (methylaluminoxane).
Suitable ionic compounds having Lewis acid cations are compounds of the formula (VIII),
where the symbols have the following meanings
Y is an element of main groups I to VI or transition groups I to VIII of the Periodic Table of the Elements,
Q1, to Qz are singly negatively charged groups such as C1-C28-alkyl, C6-C15-aryl, alkylaryl, arylalkyl, haloalkyl, haloaryl each having from 6 to 20 carbon atoms in the aryl radical and from 1 to 28 carbon atoms in the alkyl radical, C1-C10-cycloalkyl which may be unsubstituted or bear C1-C10-alkyl groups as substituents, halide, C1-C28-alkoxy, C6-C15-aryloxy, silyl or mercaptyl groups,
a is an integer from 1 to 6,
z is an integer from 0 to 5,
d is the difference axe2x88x92z, but d is greater than or equal to 1.
Particular preference is given to carbonium cations, oxonium cations and sulfonium cations and also cationic transition metal complexes. Particular mention may be made of the triphenylmethyl cation, the silver cation and the 1,1xe2x80x2-dimethylferrocenyl cation. They preferably have noncoordinating counterions, in particular boron compounds as are also mentioned in WO 91/09882, preferably tetrakis(pentafluorophenyl)borate.
Ionic compounds having Bronsted acids as cation and preferably likewise noncoordinating counterions are likewise mentioned in WO 91/09882; a preferred cation is N,N-dimethylanilinium.
The amount of activator is preferably from 0.1 to 10 equivalents, particularly preferably from 1 to 2 equivalents, for borates, based on the catalyst (VI). For alkylaluminoxanes, in particular methylaluminoxane, the amount of activator is generally from 50 to 1000 equivalents, preferably from 100 to 500 equivalents, particularly preferably from 100 to 300 equivalents, based on the catalyst (VI).
The polymerization process of the present invention is suitable for preparing homopolymers or copolymers. As unsaturated compounds or combinations of unsaturated compounds, preference is given to using unsaturated compounds selected from among ethylene, C3-C20-monoolefins, ethylene and C3-C20-monoolefins, cycloolefins, cycloolefins and ethylene and cycloolefins and propylene. Preferred C3-C20-monoolefins are propylene, butene, hexene and octene and preferred cycloolefins are norbornene, norbornadiene and cyclopentene.
The abovementioned monomers can be copolymerized with monomers containing a carbonyl group, e.g. esters, carboxylic acids, carbon monoxide and vinyl ketones. The following combinations of unsaturated compounds are preferred: ethylene and an alkyl acrylate, in particular methyl acrylate, ethylene and an acrylic acid, ethylene and carbon monoxide, ethylene, carbon monoxide and an acrylate ester or an acrylic acid, in particular methyl acrylate, and also propylene and alkyl acrylate, in particular methyl acrylate. Further suitable comonomers are acrylonitrile and styrene.
Depending on the reaction conditions and the monomers used, it is possible to obtain homopolymers, random copolymers or block copolymers by means of the process of the present invention.
The polymerization is carried out under generally customary conditions in solution, e.g. as a high-pressure polymerization in a high-pressure reactor or high-pressure autoclave, in suspension or in the gas phase (e.g. GPWS polymerization process). The appropriate polymerization processes can be carried out as batch processes, semicontinuously or continuously, with the procedures being known from the prior art.
The catalyst systems used according to the present invention can be employed in the form of all-active catalysts or supported catalysts, depending on the polymerization conditions.
As support materials, preference is given to using finely divided solids whose particle diameter is in the range of generally from 1 to 200 mm, preferably from 30 to 70 mm.
Suitable support materials are, for example, silica gels, preferably those of the formula SiO2.aAl2O3, where a is in the range from 0 to 2, preferably from 0 to 0.5; these are thus aluminosilicates or silicon dioxide. Such products are commercially available for example silica gel 332 from Grace or ES 70x from Crosfield.
To remove adsorbed water, these support materials can be subjected to a thermal or chemical treatment or be calcined; preference is given to carrying out a thermal treatment at from 80 to 200xc2x0 C., particularly preferably from 100 to 150xc2x0 C.
Other inorganic compounds such as Al2O3 or MgCl2 or mixtures comprising these compounds can likewise be used as support materials.
The catalysts of the formula (VI) can be prepared in situ and used directly, without prior isolation, in the polymerization. The catalysts can also be prepared in situ in the presence of the support material.
Suitable solvents are, in particular, aprotic organic solvents. For the catalyst system, the monomer or monomers and the polymer can be soluble or insoluble in these solvents, but the solvents should not participate in the polymerization. Examples of suitable solvents are alkanes, cycloalkanes, selected halogenated hydrocarbons and aromatic hydrocarbons. Preferred solvents are hexane, toluene and benzene; particular preference is given to toluene.
The polymerization temperatures in the solution polymerization are generally in a range from xe2x88x9220 to 350xc2x0 C., preferably from 0 to 350xc2x0 C., particularly preferably from +20 to 180xc2x0 C, very particularly preferably from room temperature to 80xc2x0 C. The reaction pressure is generally from 0.1 to 5000 bar, preferably from 0.1 to 3000 bar, particularly preferably from 1 to 200 bar, very particularly preferably from 5 to 40 bar. The polymerization can be carried out in any apparatus suitable for the polymerization of unsaturated compounds.
To control the molecular weight of the polymers, the polymerization can be carried out in the presence of hydrogen gas which acts as chain transfer reagent. The mean molecular weight usually decreases with increasing hydrogen concentration.
In addition, further auxiliaries customary in the respective polymerization process can be used.
The polymerization process of the present invention opens up a route to polyolefins having novel structures and properties. The present invention therefore further provides polymers which can be prepared by the process of the present invention.